Case 1: A 46-year-old female was admitted with sudden onset of coma. CT scan revealed brain stem and bilateral thalamic infarction. On day 3, all brain stem function was absent, while an EEG showed slow-wave activity in the frontal area. Transcranial Doppler sonography demonstrated antegrade flow in the bilateral middle cerebral arteries. Cardiac arrest occurred on day 5. Case 2: A 59-year-old male was admitted in a comatose state. A CT scan revealed a large cerebellar hematoma. Removal of the hematoma and drainage of lateral ventricle were performed, but the patient never regained brain stem function. On days 13 and 14, his condition satisfied the criteria for brain death proposed by the Japanese Ministry of Health and Welfare, except for the persistent EEG activity. Cerebral blood flow studies showed adequate blood flow in both supra and infra-tentorial regions. EEG activity was also observed on day 19. The patient experienced cardiac arrest on day 30. A state of isolated brain stem death, cessation of brain stem function accompanied by persistent EEG activity, may result from a severe cerebrovascular accident in the posterior cranial fossa. This state is usually transient, leading to total brain death, but it may continue for several days when lateral ventricular drainage is performed.
